1. Field of the Invention
The present invention relates to a musical accompaniment playing apparatus called "KARAOKE" equipment. More particularly, the present invention relates to an apparatus for multiplexing an audio signal in a video-song playback system that selectively outputs either a stereo accompaniment music or a stereo accompaniment music that includes a singer's singing voice.
2. Description of the Prior Art
At present, musical accompaniment playing apparatuses, in which one or more singers practice singing a song while looking at the words to the song's text displayed on a display screen of a display, and while being accompanied by a prerecorded music, are widespread. These musical accompaniment playing apparatuses include compact disc graphics (CDG) discs that have word data to songs, accompaniment music and graphic information recorded thereon; or disc type audio/video information recording media on which information, e.g., word data to songs, accompaniment music and moving video signals, can be massively recorded. Hereinafter, CDG discs and disc type audio/video information recording media and playback systems will be respectively designated as "video-song media" and "video-song playback systems". Each of the video-song playback systems includes an audio/video playback equipment in which a video-song medium is loaded and information, e.g., word data to songs, accompaniment music, and moving video signals, is reproduced from the loaded video-song medium. The audio/video playback equipment is operatively coupled with control equipment and with display equipment, such as a television set. The audio/video playback equipment may comprise a stand-alone-equipment or may be integrated with the control equipment. An audio amplifier is operatively coupled with the control equipment.
In the aforementioned video-song playback system, when a singer's singing voice is inputted into a voice input device, such as a microphone, in response to the song's words dam and to the accompaniment music which are reproduced from a CDG disc or a laser disc, the inputted singing voice is converted into an electrical signal. The electrical signal is amplified via an amplifier and filtered through a low pass filter, and then passes through a speaker in order to be outputted therefrom. Also, each of the video-song playback systems functions to adjust a musical interval of the accompaniment music of a selected video-song in order to double the singer's interest while practicing a video-song. Furthermore, in the video-song playback systems, while a pair of signal level detectors functions to detect the respective signal levels of both the singer's singing voice and the accompaniment music with a predetermined time interval, the signal level detectors are synchronized with each other. A microprocessor then sums up the difference in the computed signal level between the two signals until the singer's singing of a song is finished, and then a score display device displays the singing score of the singer.
As an example of the aforementioned video-song playback systems, U.S. Pat. No. 5,296,643 (issued to Jen-Wei Kuo and Tat N. Ho) discloses the configuration of a KARAOKE device that uses an automatic musical key adjustment system.
FIG. 1 is a schematic diagram for showing an example of a recording format of an audio signal on a video-song recording medium. As shown in FIG. 1, the video-song medium includes a plurality of digital audio channels and a plurality of analog audio channels. The plurality of the digital audio channels has stereo accompaniment music recorded thereon. The plurality of the analog channels includes L and R channels. The L channel has accompaniment music recorded therein and the R channel has accompaniment music including a singer's singing voice recorded therein. Therefore, playback of the accompaniment music is performed by the digital audio channels, and practice of a video-song by multiplexing of an audio signal is performed while audio levels of both the accompaniment music and the accompaniment music including a singer's singing voice recorded in the analog audio channels are adjusted in an adequate ratio in order to reproduce either the accompaniment music or the accompaniment music including a singer's singing voice.
FIG. 2 is a schematic diagram for showing another example of a recording format of an audio signal in a video-song medium. As shown in this figure, the video-song medium includes a plurality of digital audio channels and a plurality of analog audio channels. The plurality of the digital audio channels includes L channel and R channel, and the plurality of the analog audio channels also includes L and R channels. A plurality of the digital audio channels has stereo accompaniment music recorded therein, and a plurality of the analog channels has stereo accompaniment music including a singer's singing voice recorded therein. Therefore, since the L channel and the R channel have the stereo accompaniment music and the singer's singing voice recorded therein in a mixed manner, the user cannot practice a video-song in harmony either with a reproduced stereo accompaniment music or with a reproduced singer's singing voice.